CN108349244B - Ink jet printer and method of controlling ink jet printer - Google Patents

Abstract

A method of controlling an inkjet printer (40), comprising the steps of: passing the print head (200) over the print medium (300) a plurality of times to repeatedly reciprocate; -causing the nozzles to repeatedly eject (121) during each pass of the printhead (200) so that each pass results in printing a printed swath on the print medium (300); alternately deactivating the upper and lower portions of one or more nozzle arrays (202, 204, 206) on a strip-by-strip basis to reduce the height of the strip; and for each reduced-height strip, reducing the print density at the leading edge portion and the trailing edge portion of the reduced-height strip as compared to the print density at the central portion of the reduced-height strip.

Description

Inkjet printer and method of controlling inkjet printer

technical field

The present invention relates to ink jet printheads and, in particular, to methods of improving print quality.

Background technique

Traditional inkjet printing requires cyclic deposition of swaths between substrate movements. Due to many different error sources and process variables, the interfacial region of each strip (called the strip boundary) may contain defects. Examples of stripe boundary error sources are: substrate motion error, print head motion error, print head alignment, drop formation variation, ink drying time, ink colorant sequence, and so on.

One method commonly used to reduce sensitivity to substrate motion errors is tape edge tapering. This refers to reducing the stripe density of the nozzles away from the end by a certain amount, and then adjusting the movement size so that after proper substrate movement, the complementary density can be deposited by the opposite end of the printhead. A common side effect of using tape edge tapering is that new defects may be introduced due to ink colorant sequence, ink drying time, etc.

SUMMARY OF THE INVENTION

technical problem

It is an object of the present invention to reduce the effect of ink colorant order and drying time within the edge cone. This is achieved by strategically placing each tapered area relative to the preceding strip.

technical means

According to an exemplary embodiment of the present invention, an inkjet printer for applying an ink pattern to a print medium includes: a printhead including: a plurality of nozzles arranged in one or more nozzle arrays; and a controller configured to operate A printhead performs a method comprising: repeatedly reciprocating the printhead through multiple passes of the printhead over the print medium; during each printhead pass, repeatedly firing the nozzles so that each printhead pass Each pass results in printing a print band on the print medium; alternately deactivating the upper and lower part of one or more nozzle arrays, band by band, to reduce the height of the band; and for each band of reduced height , reducing the print density at the leading edge portion and the trailing edge portion of the reduced height strip compared to the print density at the central portion of the reduced height strip.

In an exemplary embodiment, two or more of the plurality of strips overlap each other to form individual rows of the ink pattern.

In an exemplary embodiment, within each row, the reduced print density leading edge portion of each reduced height strip does not extend beyond the central portion of the immediately preceding reduced height strip.

In an exemplary embodiment, the print density at the central portion of the reduced height strip is 100%.

In an exemplary embodiment, the print density at the leading and trailing edge portions of the reduced height strip tapers downward from the central portion.

Other features and advantages of embodiments of the present invention will become apparent from the following detailed description, drawings and appended claims.

Beneficial Effects of Invention

The ink jet printer according to the present invention can reduce the effects of ink colorant order and drying time within the edge cone.

Description of drawings

The features and advantages of exemplary embodiments of the present invention will be more fully understood with reference to the following detailed description, taken in conjunction with the accompanying drawings, in which:

[ Fig. 1] Fig. 1 is a perspective view of an inkjet print head according to an exemplary embodiment of the present invention;

[ Fig. 2] Fig. 2 is a perspective view of an inkjet printer according to an exemplary embodiment of the present invention;

[ Fig. 3] Fig. 3 is a layout diagram of an inkjet print head according to an exemplary embodiment of the present invention;

[ Fig. 4] Fig. 4 is a bottom plan view of an inkjet printhead according to an exemplary embodiment of the present invention;

[ Fig. 5] Fig. 5 is a perspective view showing the movement of the ink jet print head on a printing medium according to an exemplary embodiment of the present invention;

[ Fig. 6A] Fig. 6A is a side view illustrating ink ejection from a print head according to an exemplary embodiment of the present invention;

[ Fig. 6B] Fig. 6B is a side view illustrating ink ejection from a print head according to an exemplary embodiment of the present invention;

[Fig. 7] Fig. 7 shows a cross-section of the print density on four strips in sequence, how the strips are stacked at their boundaries, and the effective color order, according to a conventional printing scheme without edge tapers depiction of ; (a) shows a cross-section of the print density on four strips in sequence according to a conventional printing scheme without edge tapers, (b) shows according to a conventional printing scheme without edge tapers shows how the strips are stacked at their boundaries, (c) shows a depiction of the effective color sequence according to a traditional printing scheme without edge tapers, (d) shows a depiction of the effective color order according to a traditional printing scheme without edge tapers resulting color sequence defects;

[FIG. 8] FIG. 8 is a perspective view showing the movement of an inkjet printhead on a print medium according to a printing scheme with tapered edges and the resulting band with tapered edge print density;

[Fig. 9] Fig. 9 shows a cross-section of the print density on four strips in sequence, how the strips are stacked at their boundaries, and the effective color order according to a conventional printing scheme with edge tapers Depiction; (a) shows a cross-section of the print density on four strips in sequence according to a conventional printing scheme with edge tapers, (b) shows a strip according to a conventional printing scheme with edge tapers is how it stacks at its boundaries, (c) shows a description of the effective color order according to a traditional printing scheme with edge tapers, and (d) shows the color order defects caused by a traditional printing scheme with edge tapers ;

[ FIG. 10 ] FIG. 10 shows a cross-section of the print density on four strips in sequence, how the strips are stacked at their boundaries, and the effective color order, according to a printing scheme according to an exemplary embodiment of the present invention depiction. (a) A cross-section showing print density on four strips in sequence according to a printing scheme according to an exemplary embodiment of the present invention, (b) a printing scheme according to an exemplary embodiment of the present invention showing the strips are how they stack at their boundaries, (c) a description of the printing scheme according to an exemplary embodiment of the present invention showing the effective color order, and (d) a description of the color order resulting from the printing scheme of an exemplary embodiment of the present invention defect.

Detailed ways

The headings used herein are for organizational purposes only and are not intended to limit the scope of the description or claims. As used throughout this application, the words "may" and "could" are used in a loose sense (ie, meaning having a possibility), rather than a mandatory sense (ie, meaning must). Similarly, the words "including", "including" and variations thereof mean including but not limited to. To facilitate understanding, like reference numerals have been used, where appropriate, to refer to like elements common to the drawings.

Referring to Figure 1, an ink jet printhead is generally indicated at 10 in accordance with an exemplary embodiment of the present invention. The printhead 10 has a housing 12 made of any suitable material for containing the ink. Its shape can vary and generally depends on the external device that carries or houses the printhead. The housing has in its interior at least one compartment 16 for containing an initial or refillable ink supply. In one embodiment, the compartment has a single cavity and houses an ink supply of black ink, photosensitive ink, cyan ink, magenta ink, or yellow ink. In other embodiments, the compartment has multiple chambers, each chamber containing an independent ink supply. Preferably, it includes cyan, magenta and yellow inks. In further embodiments, the compartments contain a variety of black inks, photosensitive inks, cyan inks, magenta inks, or yellow inks. It will be appreciated that although the compartment 16 is shown partially integrated within the printhead housing 12, it may also be selectively connected to a remote ink supply and receive a supply, eg, from a conduit.

Adhered to one surface 18 of the housing 12 is a portion 19 of a flexible circuit, in particular a tape automated bonding (TAB) circuit 20 . Another portion 21 of the TAB circuit 20 is adhered to the other surface 22 of the housing. In this embodiment, the two surfaces 18 and 22 are arranged perpendicular to each other around the edge 23 of the housing.

The TAB circuit 20 supports thereon a plurality of input/output (I/O) connectors 24 for electrically connecting the heater chip 25 to devices such as printers, fax machines, copiers, Peripherals for photo printers, plotters, all-in-one devices, etc. A plurality of electrical conductors 26 are used on the TAB circuit 20 to electrically connect and short the I/O connector 24 to the input terminals (bond pads 28 ) of the heater chip 25 . Those skilled in the art are aware of a variety of techniques for facilitating such connections. For simplicity, Figure 1 shows only eight I/O connectors 24, eight electrical conductors 26, and eight bond pads 28, but currently, the number of printheads may be greater, and any number is equally included herein middle. Further, those skilled in the art will understand that although these numbers of connectors, conductors and bond pads are equal to each other, these numbers may not be equal in an actual printhead.

The heater chip 25 contains a plurality of columns 34 of fluid ejection elements for ejecting ink from the compartments 16 during use. The fluid ejection element can be implemented as a thermal resistance heating element (heater for short), which is formed as a thin film layer on a silicon substrate, or although the name based on the heater chip implies thermal technology, the fluid ejection element can also be implemented as Piezoelectric element. For simplicity, the plurality of fluid ejection elements in column 34 are shown as five points in a row adjacent to ink channel 32, but may in practice include hundreds or thousands of fluid ejection elements. As described below, vertically adjacent fluid ejection elements of the plurality of fluid ejection elements may or may not have laterally spaced gaps or staggered from each other. Typically, the fluid ejection elements have a vertical pitch interval commensurate with the dots-per-inch resolution of the printer in which they are located. Some examples include 1/300 inch, 1/600 inch, 1/1200 inch, or 1/2400 inch spacing along the length of the channel. To form this channel, various processes are known which cut or etch the channel 32 through the thickness of the heater chip. Some more preferred processes include sandblasting or etching such as wet etching, dry etching, reactive ion etching, deep reactive ion etching. The nozzle plate (not shown) has orifices therein aligned with the respective heaters to eject ink during use. The nozzle plate can be attached with adhesive or epoxy, or can be made as a thin film layer.

The memory unit 27 stores data related to information such as production date, life, and the number of refills that can be performed.

Referring to FIG. 2 , an external device in the form of an ink jet printer that houses the printhead 10 is generally indicated at 40 . The printer 40 includes a carriage 42 having a plurality of slots 44 for receiving one or more printheads 10 . As is well known in the art, carriage 42 is reciprocated along axis 48 over print zone 46 by power supplied to drive belt 50 (per output 59 of controller 57). Reciprocation of carriage 42 occurs relative to a print medium, such as a sheet of paper 52 , which travels in printer 40 along a paper path from input pallet 54 , through print area 46 , and to output pallet 56 .

When in the print zone, the carriage 42 reciprocates in a reciprocating direction generally perpendicular to the direction of travel of the paper 52 as indicated by the arrows. At such times, ink droplets from compartment 16 (FIG. 1) are caused to eject from heater chip 25 as commanded by the printer microprocessor or other controller 57. The timing of droplet ejection corresponds to the pixel pattern of the image being printed. Typically, this pattern is generated in a device electrically connected to the controller 57 (via Ext.input), which is mounted external to the printer, including but not limited to a computer, scanner, camera, visual display unit or personal data assistant, etc.

To print or eject a single drop of ink, the fluid ejection elements (dots in column 34 in Figure 1) are uniquely addressed with a small amount of current to rapidly heat a small amount of ink. This causes the ink to evaporate in the local ink chamber between the heater and the nozzle plate and be ejected through the nozzle plate towards the print medium, becoming projected by the nozzle plate. The ejection pulses required to eject such droplets may be implemented as single or separate ejection pulses based on connections between bond pads 28 , electrical conductors 26 , I/O connectors 24 and controller 57 at input terminals (e.g. , the bond pad 28) is received at the heater chip. Internal heater chip wiring delivers ejection pulses from input terminals to one or more fluid ejection elements.

Many printers are also equipped with a control panel 58 with a user selection interface 60 as input 62 to the controller 57 in order to provide additional printer capability and robustness.

FIG. 3 shows an exemplary layout of nozzles 121 in one example of printhead 112 . The printhead 112 has one or more laterally spaced nozzle or dot columns (ie, nozzle arrays). Each nozzle 121 is located at a different vertical position (where the vertical direction is the direction of travel of the print medium at right angles to the direction of travel of the print head) and corresponds to a corresponding row of pixels on the underlying print medium. In some strips of the printhead, all nozzles are used, resulting in full height stripes.

Many different printhead configurations are of course possible, and the invention is not limited to the simplified example shown in FIG. 3 . Additionally, some printheads use redundant nozzle columns for various purposes. In addition, color printers typically have three or more sets of nozzles positioned to apply ink droplets of different colors on the same row of pixels. A nozzle group can be contained within a single printhead, or it can be contained within three different printheads. The principles of the invention described herein apply to either situation.

Typically, the printheads 112 are responsive to control logic implemented by a microprocessor and memory to individually and repetitively pass the print media through the horizontal strip. The individual nozzles of the printhead are repeatedly fired during the application of the ink pattern to the print medium by each printhead strip. In some printers, the strips overlap each other so that the printhead passes each pixel row two or more times.

FIG. 4 is a representative diagram of a printhead, generally designated by reference numeral 200, in accordance with an exemplary embodiment of the present invention. The print head includes a heater chip 201 in which nozzle arrays 202, 204 and 206 are formed. Ink channels 208, 210, and 212 are provided to supply ink to nozzle arrays 202, 204, 206, respectively. The ink channels 208, 210, 212 supply different colors of ink such that each of the nozzle arrays 202, 204, 206 ejects a different color of ink. For example, ink channel 208 supplies cyan ink, ink channel 210 supplies magenta ink and ink channel 212 supplies yellow ink. For the purposes of the present invention, the X-direction corresponds to the direction in which the printhead 200 is moved laterally across the print medium to print a swath of colored ink, and the Y-direction corresponds to the relative relationship between the printhead 200 between the print medium and the swath. The direction of movement (ie, the direction of travel). As shown in FIG. 4, the nozzle arrays 202, 204, 206 extend in the Y direction, and the printhead 200 moves laterally in the X direction relative to the print medium. For further clarification, FIG. 5 is a three-dimensional diagram illustrating the movement of the printhead 200 in the X-direction relative to the print medium 300 in a plurality of strips. In an exemplary embodiment, the print medium 300 and/or the print head 200 can be moved in the Y direction so that the strips can be printed sequentially.

As the printhead 200 moves from left to right ("LTOR") and from right to left ("RTOL") on the print medium, the array of nozzles ejects ink, thereby printing strips of ink. Specifically, as shown in FIGS. 6A and 6B , when the print head 200 moves from left to right and from right to left on the print medium 300 , the heater chip 201 is properly activated to activate the nozzle arrays 202 , 204 and 206 jets ink so that cyan, magenta, and yellow inks are printed onto print medium 300 in an overlapping manner. Specifically, in the left-to-right strip, magenta ink overlaps with yellow ink, and cyan ink overlaps with magenta and yellow ink, and in right-to-left strips, magenta ink overlaps with cyan ink overlap, and the yellow ink overlaps the magenta and cyan inks.

Figure 7(a) is a schematic representation of sequential print banding on a print medium resulting from a printing scheme that does not use edge tapers to minimize color sequential and drying time defects. Each horizontal line in Figure 7(a) represents the change in print density along the y-direction on the print medium (ie, along the nozzle array) as the nozzle array prints a corresponding strip in the x-direction. As can be seen from (a) in Figure 7, for the entire strip, the print density remains constant across the nozzle array as the print head moves across the print medium. Assuming the printhead is in a two-pass mode, the printhead may alternate between left-to-right and right-to-left scanning on the print medium. Strip 1 and Strip 3 are complementary in that the leading edge of Strip 1 is aligned with the trailing edge of Strip 3. Similarly, strip 2 and strip 4 are complementary in that the leading edge of strip 2 is aligned with the trailing edge of strip 4.

As shown by the horizontal displacement of strips 1-4, the print head or media is moved a small amount between strips 1 and 2 to increase missing nozzle robustness. This introduces color sequence and drying time deficiencies. Because there is no taper (ie 100% stripe density for the entire array), a small amount of y-division error can lead to noticeable bright or dark line defects. For example, FIG. 7(b) shows the stripe stacking order, and FIG. 7(c) shows the resulting stripe stacking and color order. The portion of the print media where the bands of different colors overlap (in this example, bands 2 and 3) results in a color order defect because the primary colors are reversed. In this regard, any scale can be defined for the ink order, where 1 represents a complete reversal of the main ink order, and 0 represents complete compliance with the main ink order. As shown more clearly in (d) of FIG. 7 , the defect magnitude is greatest in the entire overlapping area because there is a complete color order reversal.

As shown in Figure 8, in order to minimize color sequence and drying time defects, edge tapers can be used. Specifically, when the print head 200 prints a strip in the X direction, the print density of the nozzle array (ie, the print density in the Y direction from the first nozzle 1 to the last nozzle N) is at the leading edge (T) and the trailing edge (T') is tapered. The leading edge (T) and trailing edge (T') are complementary because one is an inverse of the other, so when placed together, they add up to represent the full density of all pixel (or droplet) locations.

Figure 9(a) is a schematic representation of sequential print bands on a print medium resulting from a printing scheme that uses edge tapers to minimize placement errors. As mentioned earlier, tiny movements between printheads or media strips introduce color sequence and drying time defects. However, because there is a taper in the print density at the edge of each stripe (represented by the density profile in (a) in FIG. 9 and the edge of the print strip shown in (b) in FIG. 9 ) shown), so the dark and bright line defects due to y errors are reduced. In this regard, Figure 9(b) shows the strip stacking sequence and Figure 9(c) shows the resulting strip stacking and color sequence. The portion of the print media where the bands of different colors overlap resulted in a color order defect because the primary color order was reversed, but the color order defect spread by approximately twice the amount compared to a printing scheme that did not use edge tapers. As shown more clearly in (d) of FIG. 9 , the defect amplitude is not a maximum in the entire overlap region because there is a complete color order reversal only in the center of the overlap.

Although the edge tapering process reduces color order defects, the defects are not completely eliminated. In addition, the effective array length is reduced by one cone width, and since the leading edges of all strips are exposed, some drying time defects occur due to variations in ink density across the cone.

To further minimize drying time and color sequence defects, in an exemplary embodiment of the present invention (shown in FIGS. 10A-10D ), when a two-pass printing mode is implemented and tape edge tapering is used, the leading edge The second strip of tapered region is disposed on the full density portion of the first strip, rather than on top of or on top of the leading edge taper of the first strip. Doing this improves two aspects of the drying time zone: 1. It provides additional time for any drying gradients in the leading edge taper of the first strip to equilibrate (i.e. complete drying), and 2. it will give the first strip extra time to The leading edges of the two strips are positioned tapered into regions of constant density without drying gradients. Next, a third strip is deposited such that its trailing edge taper fills to complement the leading edge taper of the first strip, at which point drying is adequate. Finally, a fourth strip is deposited such that its trailing edge taper is filled to complement the leading edge taper of the second strip, at which point it is sufficiently dried. After that, the loop continues until the image is fully printed.

Figure 10(a) is a schematic representation of sequential print bands of print media produced by a printing scheme according to an exemplary embodiment of the present invention, where partially overlapping edge tapers are used to minimize color Sequence and drying time defects. Each horizontal line in (a) of FIG. 10 represents a change in print density along the y direction on the print medium (ie, along the nozzle array) when the nozzle array prints a corresponding strip in the x direction. It can be seen from (a) in FIG. 10 that the printing density remains constant over the entire nozzle array except at the edge of the array, where the printing density gradually decreases in a tapered manner. Assuming the printhead is in a dual-pass mode, the printhead may alternate between left-to-right scanning and right-to-left scanning in the print medium. Strip 1 and Strip 3 are complementary in that the bottom edge portion of Strip 1 and the top edge portion of Strip 3 form a complete strip boundary (ie, at the bottom edge portion of Strip 1 and the top edge of Strip 3 only a portion of the full strip border is printed in each of the edge sections), and strips 2 and 4 are complementary in that the bottom edge section of strip 2 and the top edge section of strip 4 form a complete strip Boundaries (ie, only a portion of the full stripe boundary is printed in each of the bottom edge portion of strip 2 and the top edge portion of strip 4).

The printhead or media is moved a small amount between strips to increase missing nozzle robustness. Additionally, this introduces small color sequence and drying time deficiencies. However, due to the taper in the print density at the edge of each stripe, dark and light line defects due to y-errors are reduced. Furthermore, the nozzles are alternately not used starting from each end of the nozzle array. For example, nozzles at the trailing edge of the nozzle array may be unused in odd-numbered print swaths, and nozzles at the leading edge of the nozzle array may be unused in even-numbered print swaths. This results in the leading edge of the even numbered strip being pulled back over the 100% density printed portion of the previous strip.

Figure 10(b) shows the stripe stacking sequence, and Figure 10(c) shows the resulting stripe stacking and color sequence resulting from a tapered printing scheme according to an exemplary embodiment of the present invention. The portion of the print media where the bands of different colors overlap resulted in a color order defect because the primary color order is reversed, but the color order defect is further reduced compared to printing schemes that use edge tapers. As shown more clearly in (d) of Figure 10, due to the taper and overlap, the color order is not completely reversed because only edge tapers are used and not edge tapers are used in the printing scheme. Compared to using cone alone, the color sequential defect area is reduced by 50% and therefore the peak defect magnitude is also reduced by 50%.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended to cover in the appended claims all such changes and modifications as come within the scope of this invention.

List of reference signs

10, 112, 200: print head

12: Shell

16: Compartment

18, 22: Surface

19, 21: Parts

20: TAB circuit

23: Edge

24: I/O connector

25: Heater chip

26: Electrical conductors

27: Memory Unit

28: Bond pads

32: Ink channel

34: Columns

40: Printer

42: Sliding rack

44: Slot

46: print area

48: Shaft

50: Drive belt

52: Paper

54: Input pallet

56: Output pallet

57: Controller

58: Control Panel

59: output

60: User selection interface

62: Input

121: Nozzle

201: Heater Chip

202, 204, 206: Nozzle array

208, 210, 212: Ink channel

300: print media

Claims (6)

1. An ink jet printer that applies an ink pattern to a print medium, the ink jet printer comprising: a printhead, comprising: a plurality of nozzles arranged in one or more nozzle arrays; and a controller configured to operate the printhead to perform a method, the method comprising: passing the printhead over the print medium multiple times to repeatedly reciprocate; repeating the firing of the nozzles during each pass of the printhead such that each pass results in a print band being printed on the print medium; tapering the leading and trailing edge portions of each strip; and reducing the print density at the tapered leading and trailing edge portions of the strip compared to the print density at the central portion of the strip; wherein a second strip of the plurality of strips overlaps the first strip, and a fourth strip overlaps the third strip to form individual rows of the ink pattern; wherein, within each row, the reduced print density leading edge portion of the second strip does not extend beyond the central portion of the first strip, and the fourth strip reduced print density leading edge portion does not extend beyond the central portion of said third strip; Within each row, the leading edge portion of the first strip and the trailing edge portion of the third strip form a strip boundary, and the leading edge portion of the second strip and the fourth strip The trailing edge portion forms the strip boundary. 2. The ink jet printer of claim 1, wherein the print density at the central portion of the strip is 100%. 3. The ink jet printer of claim 1 or 2, wherein the print density at the leading and trailing edge portions of the strip tapers downward from the central portion. 4. A method of controlling an inkjet printer comprising a printhead having a plurality of nozzles arranged in one or more nozzle arrays to produce a print band on a print medium , the method includes the following steps: passing the printhead over the print medium multiple times to repeatedly reciprocate; repeating the firing of the nozzles during each pass of the printhead such that each pass results in a print band being printed on the print medium; tapering the leading and trailing edge portions of each strip; and reducing the print density at the tapered leading and trailing edge portions of the strip compared to the print density at the central portion of the strip; wherein a second strip of the plurality of strips overlaps the first strip, and a fourth strip overlaps the third strip to form individual rows of the ink pattern; wherein, within each row, the reduced print density leading edge portion of the second strip does not extend beyond the central portion of the first strip, and the fourth strip reduced print density leading edge portion does not extend beyond the central portion of said third strip; Within each row, the leading edge portion of the first strip and the trailing edge portion of the third strip form a strip boundary, and the leading edge portion of the second strip and the fourth strip The trailing edge portion forms the strip boundary. 5. The method of claim 4, wherein the print density at the central portion of the strip is 100%. 6. The method of claim 4 or 5, wherein the print density at the leading and trailing edge portions of the strip tapers downwardly from the central portion.

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